This invention relates to medical and surgical devices and in particular to medical and surgical devices used in conjunction with patient respiration problems. More specifically, this invention relates to a means for providing an airway for patients requiring mechanical assistance in breathing, and/or for conduction of anesthetic gas when a tube is placed in the trachea through the mouth, nose or during a tracheostomy.
In any situation where ventilatory support to control respiration is necessary, the use of cuffed preformed tracheal tubes, whether by oral--translaryngeal insertion or by placement through a tracheostomy, has become the standard of medical practice. Additionally, by means of the inflatable cuff placed distally on the tube and expanded with sufficient pressure against the tracheal wall to form a seal, the tracheobronchial tubes are protected from aspiration of gastric contents or other foreign matter. These devices are the essential means of controlling the exchange of blood gases by establishing a closed system whereby the gas pressure in the airway distal to the inflated cuff can be maintained at the desired level. These essential functions of cuffed preformed tracheal tubes are used during the delivery of anesthetic gases or oxygen in critical intensive care situations. This closed system of pulmonary ventilation is possibly the most important advance in modern anesthesia and in the care of the critically ill or trauma victim. Regardless of advances the future may bring in these areas, control of respiration will always be necessary and the use of the tracheal tubes as a conduit between the lungs and the extracorporeal support system will always be required.
Presently used tracheal tubes have several known design and functional deficiencies which create significant complications in their use. The more severe of these problems are related to the inflatable cuff and are directly proportional to: (1) the pressure within the cuff necessary to occlude the trachea to maintain respiration and (2) the duration of tracheal intubation. As cuff pressure exceeds the capillary pressure of the tracheal tissues, normally 25 mm of mercury, tissue anoxia occurs and varying degrees of tracheal injury result. The injuries range from mild erosion of the mucosa, to destruction of the tracheal cartilage rings, to segmental tracheomalacia with dilatation of the trachea. More dramatic is full thickness erosion, with perforation of the inominate artery anteriorly or posteriorly into the esophagus; either of these events being associated with a high rate of mortality. Late complications of tracheal stenosis, from mild to incapacitating obstruction are noted in the majority of patients requiring long term ventilatory support.
An attempt at solving the above-mentioned Problems is disclosed in my prior U.S. Pat. Nos. 4,340,046 and 4,471,776, both of which are fully incorporated herein by reference. These prior patents describe an improved tracheostomy tube having four distinctive features including a precision cuff fitted to each trachea, a flexible tube that will conform to any depth of the trachea within the neck, a self-locking clip that adjusts the tube securely to an neck regardless of the depth of the trachea, and a malleable but rigid obturator for ease of insertion.
The precision cuff of my prior patents is fitted to each trachea. The cuff of tracheal tubes of the prior art are not provided with this feature. Most tracheal tubes that are in use now and in the prior art have a soft cuff that, when inflated, assumes a fusiform shape presenting a narrow surface in contact with the trachea mucosa. Any prolonged pressure above twenty-five torr increases the risk of tracheal necrosis. In my prior patents, the improved precision cuff comprises a substantially convoluted or fluted cuff with constricting bands to limit distention to the specific size of each trachea.
The advantage of the precision convoluted-like or fluted cuff of my prior patents is to equalize the pressure over a longer segment of the mucosa by the use of the constricting bands limiting the size in the cuff constrictions. This also insures uniform diameter and controlled expansion.
The convoluted-like or fluted cuff and the manner of assuring the precise size in relation to the patient's trachea, effects a more complete seal at a lower pressure on the tracheal mucosa. Each convolution-like roll or flute creates a seal and the plurality of seals increases the total sealing effectiveness, thus avoiding the problem of the fusiform configuration which is inherent in the single chamber cuff.
While well suited for its intended purposes, the fluted cuff of my prior patents suffers from certain drawbacks and deficiencies and a need exists for an improved tracheal tube cuff.